During the normal operation of a computer, integrated circuit devices generate significant amounts of heat. This heat must be continuously removed, or the integrated circuit device may overheat, resulting in damage to the device and possibly a reduction in operating performance. Cooling devices, such as heat sinks, have been used in conjunction with integrated circuit devices in order to avoid such overheating. Generally, a passive heat sink in combination with a system fan has provided a relatively cost-effective cooling solution. In recent years, however, the power of integrated circuit devices such as microprocessors has increased exponentially, resulting in a significant increase in the amount of heat generated by these devices, thereby necessitating a more efficient cooling solution.
It is becoming extremely difficult to extract the heat generated by semiconductor devices (processors, in particular) that continue to generate more and more heat in the same amount of space. Heat is typically extracted by coupling a heat spreader and thermal cap to the semiconductor and a heat sink. This coupling typically involves a thermal paste which serves to not only transfer heat but provide some degree of mechanical compliance to compensate for dimensional changes driven by the high temperatures. This paste is often a weak link in the thermal path. Attempts to thin this layer have resulted in failure of the layer when it is exposed to dimensional changes due to heat.
One approach to this problem involves a spring loaded assembly of fingers with thermal paste in between them and a thermal paste interface to the chip. This solution is limited in performance by the thermal paste and in design by the requirement for consistent spring loading. Liquid metal has been proposed on its own as a thermal interface material, but could have significant difficulty dealing with large z-axis thermally induced excursions, requiring some compliance elsewhere in the package or (if the largest spacing seen is still thermally acceptable) some sort of edge reservoir design.
Another approach to this problem involves the use of silicon based liquid or vapor chamber coolers coupled with solid thermal interface materials (like solders). Performance of these coolers, however, can be impacted by the relatively low thermal conductivity of silicon. As there is little to no compliance in the coolers, the choice of thermal interface material is limited. Yet another proposed solution is a compliant (either locally or globally or both) thermal cap that allows for much thinner thermal interface materials. These solutions, however, typically still insert a significant thermal resistance between the semiconductor and the heat sink or liquid cold cap, which is disadvantageous.
Therefore, a need exists to overcome the problems with the prior art as discussed above, and particularly for a way to cool small electronic devices using a thermally compliant material.